This invention relates to a clamping device for a holder of a disc playback device of a type having a holder for holding a disc or a disc cartridge case receiving a disc and being capable of displacing the holder between a position in which the disc is not played back and a position in which the disc is played back and, more particularly, to a clamping device of such type being capable of accurately clamping the holder in position when the holder has been displaced to the disc playback position.
The applicant of the present invention has previously proposed a disc playback device for playing back a disc such as a disc for the Compact Disc Digital Audio System as shown in FIGS. 8 and 9 (the U.S. patent application Ser. No. 781,768) filed Sept. 30, 1985.
Referring to FIGS. 8 and 9, the proposed disc playback device consists of a disc cartridge case A and a main body B. A disc is housed in the disc cartridge case A and this disc cartridge case A is loaded in the main body B and the disc is played back in a state in which it is housed in the disc cartridge case A.
The disc cartridge case A is provided on one side thereof with a rack (not shown) for loading the case A in the main body B.
Above a chassis 1 of the main body B, there are provided a turntable 3 driven by a disc driving motor 2, a carrier 4 and a holder 5. Below the chassis 1, there is provided an optical pickup head device 6. The carrier 4 is movable in directions shown by arrows P1, P2 by an unillustrated drive source. The holder 5 which is provided for holding the disc cartridge case A is movable vertically along pins 7, 7 . . . fixedly secured to the chassis 1 and is constantly urged downwardly by connection springs 8, 8 . . . provided between the holder 5 and the chassis 1. In a state shown in FIG. 8, the holder 5 is in its elevated position with its cams 9, 9 . . . formed on the lower surface thereof being in abutting contact with the upper surface of the carrier 4. As the carrier 4 is moved in the direction of arrow P1, the holder 5 is gradually moved downwardly by entering of the cams 9, 9 . . . into openings (not shown) formed in the chassis 1. A loading pinion 10 is provided on the chassis 1 in such a manner that it is rotated in association with the movement of the carrier 4 and is brought into meshing engagement with the rack of the disc cartridge case A, causing this case A to move in the direction of arrows P1, P2.
For playing back a disc 11 by the main body B, the disc cartridge case A housing the disc 11 is manually inserted into a predetermined position in the direction of arrow P1 in the holder 5. At this time, the holder 5 is in the elevated position shown in FIG. 8. Upon detection of the insertion of the disc cartridge case A in the predetermined position in the holder 5, the carrier 4 starts its movement in the direction of arrow P1 by means of its driving system. This in turn causes the loading pinion 10 to be rotated and come into meshing engagement with the rack of the disc cartridge case A thereby causing the case A to be moved in the direction of arrow P1. As the disc cartridge case A is moved to a region above the turntable 3, the cams 9, 9 . . . of the holder 5 gradually enter the openings of the carrier 4 and the chassis 1, and the holder 5 is moved downwardly by the urging force of the connection springs 8, 8 . . . while holding the disc cartridge case A therein. As the holder 5 and the disc cartridge case A are moved downwardly, the turntable 3 enters in a relative movement into the disc cartridge case A through an opening (not shown) formed in the disc cartridge case A and the disc 11 housed in the case A thereby is mounted on the turntable 3. The drive source of the carrier 4 thereupon is stopped and the loading of the disc cartridge case A is completed. If a playback command is given to the main body B in this state, the disc driving motor 2 is started to rotate the turntable 3 with the disc 11 and the disc 11 is played back with the optical pickup head device 6 picking up signals recorded on the disc 11.
The disc playback device described above is constructed such that, when the holder 5 and the disc cartridge case A have been moved downwardly to the position in which the disc 11 can be played back, the force for clamping the holder 5 is obtained by the urging force of the connection springs 8, 8 . . . In this construction, however, the connection springs 8, 8 . . . which were initially in an expanded state become unexpanded when the holder 5 has been moved to its lowered position. This reduces the clamping force of the connection springs 8, 8 . . . with a resulting insecurity in clamping of the holder 5. This gives rises to inconvenience such as an undesired vertical movement of the holder 5 due to vibrations occurring outside of the device. Thus, the above described disc playback device is not satisfactory in the antivibration characteristics of the holder 5. Besides, when the disc cartridge case A is loaded in or ejected from the main body B, the cams 9, 9 . . . of the holder 5 are brought into abutting engagement with the carrier 4 in a state in which the connection springs 8, 8 . . . are strongly pulled so that friction between the carrier 4 and the cams 9, 9 . . . causes load of a large value to be imposed upon the drive source of the carrier 4.